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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 11th Jul 2017, 5:24 pm   #1
Telegraph-Hill
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Default General Questions about old Record Player Motors

Hello Forum.

first of all thanks for putting all this useful informations together in this forum.

After repairing 50-60 old record players in the last 2.5 Years I do come across some interesting problems. At the moment I'm servicing a Pye black box.

I come across some players spinning not to the exact speed (slower). Doing everything possible to resolve problems like greasing (Motor and mechanic), cleaning the inside of the turntable platter and even recondition some very hard Idler wheels (not just only using liquids or just raw the surface with sandpaper) I still have some player left me with this problem.

What seems to be equal on all this faults is the fact that the motors are running quite hot. (hotter than just handwarm). The same problem I have also on my Pye at the moment. (63 degrees Celsius)

The only logical explanation for me seems, that some windings in the motor have shorteD, increasing the current and letting the motor running slower.

What do you think, can this be the case? Or am I on the wrong route?

Sorry for my bad English but it is not my native language.

Cheers, Oliver.

Last edited by Telegraph-Hill; 11th Jul 2017 at 5:47 pm.
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Old 11th Jul 2017, 5:40 pm   #2
Edward Huggins
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Default Re: General Questions about old Record Player Motors

On the BSR UA6, BSR UA8 and even later BSR UA15 autochanger models, there was always a + or - speed variation of around 4-6%. After all, these were quite basic turntales. On the single play models, the Collaro deck will be slightly more accurate as these were better made.
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Old 11th Jul 2017, 6:02 pm   #3
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Default Re: General Questions about old Record Player Motors

I would have thought that if it was shorted turns you would get extreme overheating from the shorted turns with smoke. Does the motor spindle spin perfectly freely when you turn it by hand? Plain bearings should not be greased in these motors but use light oil to lubricate. Grease will cause drag and over time could cause bearing to sieze as grease breaks down
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Old 11th Jul 2017, 6:15 pm   #4
Telegraph-Hill
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Default Re: General Questions about old Record Player Motors

I guess we are talking about just about a couple of turns getting shorted. Otherwise, you are right, it will smoke

I did not find a big difference between grease (I'm using a grease we have used in old IBM machines) and Oil. With Oil I found out that it will evaporate after a time. I had some machines in my workshop have been originally greased and got hardened (after 30+ years) and machines without any grease. In the very long run I would prefer no, or only very light greasing at all.
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Old 11th Jul 2017, 7:02 pm   #5
TonyDuell
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Default Re: General Questions about old Record Player Motors

Have you checked that motors that run at the right speed do not get over-hot?

A shaded pole motor (which a lot of cheaper record player motors are) naturally runs hot. The shading links act as shorted turns.

Have you tried to measure the speed of the motor directly (that is, 'before' any belts, idlers, speed change arrangements, etc), perhaps with an adjustable strobe lamp. That would tell you if the motor was running slow.
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Old 11th Jul 2017, 7:45 pm   #6
Restoration73
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Default Re: General Questions about old Record Player Motors

Garrard made motors for 60Hz, 50Hz, and 40Hz mains frequencies, this is not always
indicated on the motor or deck.
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Old 11th Jul 2017, 8:30 pm   #7
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Default Re: General Questions about old Record Player Motors

Quote:
Originally Posted by Edward Huggins View Post
On the BSR UA6, BSR UA8 and even later BSR UA15 autochanger models, there was always a + or - speed variation of around 4-6%. After all, these were quite basic turntales. On the single play models, the Collaro deck will be slightly more accurate as these were better made.
I would agree with everything Edward has said. All my BSR turntable machines do run ever so slightly fast probably within the margins Edward has quoted.
The motors on mine do get quite warm but spin very freely. A couple of my cheaper record players also have a winding on the motor to supply voltage to the amplifier so maybe this generates a bit of extra heat.
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Old 11th Jul 2017, 8:30 pm   #8
Telegraph-Hill
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Default Re: General Questions about old Record Player Motors

Quote:
Originally Posted by TonyDuell View Post
Have you checked that motors that run at the right speed do not get over-hot?
At the moment I do not have the same motor to compare but 63 degrees after 1h of operation seems to be quite hot.

Quote:
Have you tried to measure the speed of the motor directly (that is, 'before' any belts, idlers, speed change arrangements, etc), perhaps with an adjustable strobe lamp. That would tell you if the motor was running slow.
That would be the evidence. But unfortunately here we have the same problem, not having another same style motor to compare. Also Shaded Motors have a constant speed but it is not graved in stone what speed they should have. It all depends on Rotor, coil and size.

Cheers,
Oliver
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Old 12th Jul 2017, 5:23 pm   #9
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Default Re: General Questions about old Record Player Motors

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Originally Posted by Telegraph-Hill View Post
Also Shaded Motors have a constant speed but it is not graved in stone what speed they should have. It all depends on Rotor, coil and size.

No they don't. They're just a single phase induction motor with a bit of phase shifted field provided by the pole shading to enable them to self start. Increased load will result in greater slip and lower running speed up to the point of stall. Synchronous motors run at a constant speed until load reaches max holding torque, then just stall. There are hybrids (Synduction?) which not surprisingly run at constant speed up to rated torque then stall somewhat more gently. ISTR the SP25 mkIV had something of the sort.
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